Linux内核数据结构之链表list.h详解
#ifndef _LINUX_LIST_H
#define _LINUX_LIST_H
#include <linux/types.h>
#include <linux/stddef.h>
#include <linux/poison.h>
#include <linux/const.h>
/*
* Simple doubly linked list implementation. 简单的双向链表实现
*
* //当我们操作双循环链表而不是单链表时，有些内部函数很有用。
* //当我们已经知道前驱/后继结点时，我们可以直接利用这些函数
* //生成更优秀的代码生成更优秀的代码而不是用一般的单链表操作
*
* Some of the internal functions ("__xxx") are useful when
* manipulating whole lists rather than single entries, as
* sometimes we already know the next/prev entries and we can
* generate better code by using them directly rather than
* using the generic single-entry routines.
*/
struct list_head{
struct list_head *next, *prev;
};
/********************宏初始化链表********************/
//定义+初始化
#define LIST_HEAD_INIT(name) { &(name), &(name) }
//头指针name初始化
#define LIST_HEAD(name) \
struct list_head name = LIST_HEAD_INIT(name)
//初始化，空链表
static inline void INIT_LIST_HEAD(struct list_head *list)
{
list->next = list;
list->prev = list;
}
/*
* //在两个连续的结点之间插入一个新的结点
* Insert a new entry between two known consecutive entries.
*
* //下面仅仅是我们对内部的已知前驱/后继结点的链表的操作
* This is only for internal list manipulation where we know
* the prev/next entries already!
*/
/**********************************************************************************************************/
/**************************************************插入****************************************************/
/**********************************************************************************************************/
#ifndef CONFIG_DEBUG_LIST
static inline void __list_add(struct list_head *new,
struct list_head *prev,
struct list_head *next)
{
next->prev = new;
new->next = next;
new->prev = prev;
prev->next = new;
}
#else
extern void __list_add(struct list_head *new,
struct list_head *prev,
struct list_head *next);
#endif
/*
* list_add - add a new entry //list_add - 头插
* @new: new entry to be added //@new: 要插入的新结点
* @head: list head to add it after //@head: 链表的头，插入到这个结点之后
*
* //新结点插入到指定头结点之后
* Insert a new entry after the specified head.
* 这是堆栈的一个很好的实现
* This is good for implementing stacks.
*/
/***********************************************头插*******************************************************/
static inline void list_add(struct list_head *new, struct list_head *head)
{
__list_add(new, head, head->next);
}
/**
* list_add_tail - add a new entry //list_add_tail - 尾插
* @new: new entry to be added //@new: 要插入的新结点
* @head: list head to add it before //@head:链表的头，插入到这个结点之前
*
* //在指定的结点之前插入一个结点
* Insert a new entry before the specified head.
* This is useful for implementing queues.
*/
/***********************************************尾插*******************************************************/
static inline void list_add_tail(struct list_head *new, struct list_head *head)
{
__list_add(new, head->prev, head);
}
/*
* //通过让一个结点的前驱/后继结点相互指向对方来删除一个结点
*
* Delete a list entry by making the prev/next entries
* point to each other.
*
* This is only for internal list manipulation where we know
* the prev/next entries already!
*/
/**********************************************************************************************************/
/***********************************************删除*******************************************************/
/**********************************************************************************************************/
static inline void __list_del(struct list_head * prev, struct list_head * next)
{
next->prev = prev;
prev->next = next;
}
/**
* list_del - deletes entry from list. //list_del - 从链表删除结点
* @entry: the element to delete from the list. //@entry: 要从链表删除的结点
* //@Note:
* Note: list_empty() on entry does not return true after this, the entry is
* in an undefined state.
*/
#ifndef CONFIG_DEBUG_LIST
static inline void __list_del_entry(struct list_head *entry)
{
__list_del(entry->prev, entry->next);
}
/*
* LIST_POISON1和LIST_POISON2这两个变量在poison.h中定义的：
* #define LIST_POISON1 ((void *) 0x00100100 + POISON_POINTER_DELTA)
* #define LIST_POISON2 ((void *) 0x00200200 + POISON_POINTER_DELTA)
* prev、next指针分别被设为LIST_POSITION2和LIST_POSITION1两个特殊值
* 这样设置是为了保证不在链表中的节点项不可访问
*(对LIST_POSITION1和LIST_POSITION2的访问都将引起页故障)
*/
static inline void list_del(struct list_head *entry)
{
__list_del(entry->prev, entry->next);
//entry置为不可用
entry->next = LIST_POISON1;
entry->prev = LIST_POISON2;
}
#else
extern void __list_del_entry(struct list_head *entry);
extern void list_del(struct list_head *entry);
#endif
/*
* list_replace - replace old entry by new one //list_replace - 结点更新
* @old : the element to be replaced //@old ：要被替换的结点
* @new : the new element to insert //@new : 新结点
*
* If @old was empty, it will be overwritten. //如果旧结点是个空结点，将会被覆盖
*/
/**********************************************************************************************************/
/***********************************************替换*******************************************************/
/**********************************************************************************************************/
//old置为不可用
static inline void list_replace(struct list_head *old,
struct list_head *new)
{
new->next = old->next;
new->next->prev = new;
new->prev = old->prev;
new->prev->next = new;
}
static inline void list_replace_init(struct list_head *old,
struct list_head *new)
{
list_replace(old, new);
//old置为空链表
INIT_LIST_HEAD(old);
}
/**
* //list_del_init - 从链表删除结点并初始化该结点为空链表
* list_del_init - deletes entry from list and reinitialize it.
* @entry: the element to delete from the list. //@entry : 从链表删除的结点
*/
static inline void list_del_init(struct list_head *entry)
{
__list_del_entry(entry);
//置entry为空链表
INIT_LIST_HEAD(entry);
}
/**********************************************************************************************************/
/***********************************************移动*******************************************************/
/**********************************************************************************************************/
/*********************************************移动头插*****************************************************/
/**
* list_move - delete from one list and add as another's head //list_move - 从一个链表移除并且用头插法插入到另一个链表
* @list: the entry to move //@list : 要移除的结点
* @head: the head that will precede our entry //@head : 插入到head结点之后
*/
static inline void list_move(struct list_head *list, struct list_head *head)
{
__list_del_entry(list);
list_add(list, head);
}
/*********************************************移动尾插*****************************************************/
/**
* list_move_tail - delete from one list and add as another's tail //list_move_tail - 从一个链表移除结点，并用尾插法把该结点插入到另一个链表
* @list: the entry to move //@list : 要移除的几点
* @head: the head that will follow our entry //@head : head为该结点后继
*/
static inline void list_move_tail(struct list_head *list,
struct list_head *head)
{
__list_del_entry(list);
list_add_tail(list, head);
}
/**********************************************************************************************************/
/***************************************************检测***************************************************/
/**********************************************************************************************************/
/**
* list_is_last - tests whether @list is the last entry in list @head //list_is_last - 测试 以 head 开头的链表的list 结点
* @list: the entry to test //@list ：要测试的结点
* @head: the head of the list //@head : 链表的头
*/
/*******************************************判断是否是最后一个结点******************************************/
static inline int list_is_last(const struct list_head *list,
const struct list_head *head)
{
return list->next == head;
}
/***************************************判断 head 这个链表是不是空链表***************************************/
/*
* list_empty()函数和list_empty_careful()函数都是用来检测链表是否为空的。但是稍有区别的就是第一个链表使用的检测方法是
* 判断表头的结点,的下一个结点是否为其本身，如果是则返回为1，否则返回0。第二个函数使用的检测方法是判断表头的前一个结点
* 和后一个结点是否为其本身，如果同时满足则返回0，否则返回值为1。
*
* 这主要是为了应付另一个cpu正在处理同一个链表而造成next、prev不一致的情况。但代码注释也承认，这一安全保障能力有限：
* 除非其他cpu的链表操作只有list_del_init()，否则仍然不能保证安全，也就是说，还是需要加锁保护。
*/
/**
* list_empty - tests whether a list is empty
* @head: the list to test.
*/
static inline int list_empty(const struct list_head *head)
{
return head->next == head;
}
/**
* list_empty_careful - tests whether a list is empty and not being modified
* @head: the list to test
*
* Description:
* tests whether a list is empty _and_ checks that no other CPU might be
* in the process of modifying either member (next or prev)
*
* NOTE: using list_empty_careful() without synchronization
* can only be safe if the only activity that can happen
* to the list entry is list_del_init(). Eg. it cannot be used
* if another CPU could re-list_add() it.
*/
static inline int list_empty_careful(const struct list_head *head)
{
struct list_head *next = head->next;
return (next == head) && (next == head->prev);
}
/*
/**
* list_rotate_left - rotate the list to the left //向左旋转
* @head: the head of the list
*/
//旋转链表第一个结点到最后
static inline void list_rotate_left(struct list_head *head)
{
struct list_head *first;
if (!list_empty(head)) {
first = head->next;
list_move_tail(first, head);
}
}
/********************************判断 head 这个链表是否只有一个结点(除了head)********************************/
/**
* list_is_singular - tests whether a list has just one entry.
* @head: the list to test.
*/
//返回1，有一个结点
static inline int list_is_singular(const struct list_head *head)
{
return !list_empty(head) && (head->next == head->prev);
}
/************************************************************************************************************/
/**************************************************分割链表**************************************************/
/************************************************************************************************************/
/*
* _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
* | _ _ _ _ _ _ _ _ |
* ---| |->| |->| |->| |->| |->| |->| |->| |<--|
* ---->|_|<-|_|<-|_|<-|_|<-|_|<-|_|<-|_|<-|_|------|
* | head entry |
* |_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|
*
* _
* | |
* |_|
* list
*/
/********************************************head 与 entry 不重合*******************************************/
/*
* @list : 链表外的一个结点
* @head : 以 head 开始的链表
* @entry : 以 head 开始的链表中的一个结点
*/
static inline void __list_cut_position(struct list_head *list,
struct list_head *head, struct list_head *entry)
{
struct list_head *new_first = entry->next;
list->next = head->next;
list->next->prev = list;
list->prev = entry;
entry->next = list;
head->next = new_first;
new_first->prev = head;
}
/********************************************head 与 entry 重合********************************************/
/**
* list_cut_position - cut a list into two
* @list: a new list to add all removed entries
* @head: a list with entries
* @entry: an entry within head, could be the head itself
* and if so we won't cut the list
*
* This helper moves the initial part of @head, up to and
* including @entry, from @head to @list. You should
* pass on @entry an element you know is on @head. @list
* should be an empty list or a list you do not care about
* losing its data.
*
*/
static inline void list_cut_position(struct list_head *list,
struct list_head *head, struct list_head *entry)
{
if (list_empty(head))
return;
if (list_is_singular(head) &&
(head->next != entry && head != entry))
return;
if (entry == head)
//entry 指向 head ，无法分割，初始化list为一个空链表
INIT_LIST_HEAD(list);
else
//生成两个链表，head 和 list
__list_cut_position(list, head, entry);
}
/************************************************************************************************************/
/**************************************************链表合并**************************************************/
/************************************************************************************************************/
/*
* _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
* | _ _ _ _ _ _ _ _ |
* ---| |->| |->| |->| |->| |->| |->| |->| |<--|
* ---->|_|<-|_|<-|_|<-|_|<-|_|<-|_|<-|_|<-|_|------|
* | list |
* |_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|
*
* _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
* | _ _ _ _ _ _ _ _ |
* ----| |->| |->| |->| |->| |->| |->| |->| |<--|
* ---->|_|<-|_|<-|_|<-|_|<-|_|<-|_|<-|_|<-|_|------|
* | prev next |
* |_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|
*/
/*************************************************链表合并算法**********************************************/
//不包括list这个结点
static inline void __list_splice(const struct list_head *list,
struct list_head *prev,
struct list_head *next)
{
struct list_head *first = list->next;
struct list_head *last = list->prev;
first->prev = prev;
prev->next = first;
last->next = next;
next->prev = last;
}
/**************************************list链表以头插的方式插入head链表**************************************/
/**
* list_splice - join two lists, this is designed for stacks
* @list: the new list to add.
* @head: the place to add it in the first list.
*/
static inline void list_splice(const struct list_head *list,
struct list_head *head)
{
if (!list_empty(list))
__list_splice(list, head, head->next);
}
/**************************************list链表以尾插的方式插入head链表**************************************/
/**
* list_splice_tail - join two lists, each list being a queue
* @list: the new list to add.
* @head: the place to add it in the first list.
*/
// 注意：插入后，list->prev 将会是原来的 list->prev
static inline void list_splice_tail(struct list_head *list,
struct list_head *head)
{
if (!list_empty(list))
__list_splice(list, head->prev, head);
}
/**************************list链表以头插的方式插入head链表，并初始化 list 为空链表**************************/
/**
* list_splice_init - join two lists and reinitialise the emptied list.
* @list: the new list to add.
* @head: the place to add it in the first list.
*
* The list at @list is reinitialised
*/
static inline void list_splice_init(struct list_head *list,
struct list_head *head)
{
if (!list_empty(list)) {
__list_splice(list, head, head->next);
INIT_LIST_HEAD(list);
}
}
/**************************list链表以尾插的方式插入head链表，并初始化 list 为空链表**************************/
/**
* list_splice_tail_init - join two lists and reinitialise the emptied list
* @list: the new list to add.
* @head: the place to add it in the first list.
*
* Each of the lists is a queue.
* The list at @list is reinitialised
*/
//注意：插入后，list->prev 将会是原来的 list->prev
static inline void list_splice_tail_init(struct list_head *list,
struct list_head *head)
{
if (!list_empty(list)) {
__list_splice(list, head->prev, head);
INIT_LIST_HEAD(list);
}
}
/************************************************************************************************************/
/*****************************************************宏*****************************************************/
/************************************************************************************************************/
/****************************************************offsetof************************************************/
/*********************************************求结构内成员地址偏移量*****************************************/
//myread_linux-3.5/include/linux/stddef.h
/*
* 1.( (TYPE *)0 ) 将零转型为TYPE类型指针;
* 2.((TYPE *)0)->MEMBER 访问结构中的数据成员;
* 3.&( ( (TYPE *)0 )->MEMBER )取出数据成员的地址;
* 4.(size_t)(&(((TYPE*)0)->MEMBER))结果转换类型。
* 5.巧妙之处在于将0转换成(TYPE*)，结构以内存空间首地址0作为起始地址，则成员地址自然为偏移地址；
*/
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
/***************************************************container_of**********************************************/
/****************************************通过指针ptr.返回结构体起始地址***************************************/
//myread_linux-3.5/drivers/staging/rtl8192e/rtllib.h
#ifndef container_of
/**
* container_of - cast a member of a structure out to the containing structure
*
* //ptr指向type成员member
* @ptr: the pointer to the member. //@ptr : 指向成员的指针
* @type: the type of the container struct this is embedded in. //@type : 结构(体)类型
* @member: the name of the member within the struct. //member : 结构(体)内成员名
*
* typeof是GNU C对标准C的扩展，它的作用是根据变量获取变量的类型。因此，下面代码中的第2行的作用是首先
* 使用typeof获取结构体域变量member的类型为 type，然后定义了一个type指针类型的临时变量__mptr，并将实
* 际结构体变量中的域变量的指针ptr的值赋给临时变量__mptr
*
* 1.(char *)__mptr转换为字节型指针。
* 2.(char *)__mptr - offsetof(type,member) )用来求出结构体起始地址（为char *型指针），
* 3.然后(type *)( (char *)__mptr - offsetof(type,member) )在(type *)作用下进行将字节型的结构体起始指针转换为type *型的结构体起始指针。
*/
#define container_of(ptr, type, member) ({ \
const typeof(((type *)0)->member)*__mptr = (ptr); \
(type *)((char *)__mptr - offsetof(type, member)); })
#endif
/****************************************************list_entry***********************************************/
/**
* list_entry - get the struct for this entry
* @ptr: the &struct list_head pointer.
* @type: the type of the struct this is embedded in.
* @member: the name of the list_struct within the struct.
*/
#define list_entry(ptr, type, member) \
container_of(ptr, type, member)
/************************************************list_first_entry********************************************/
/**
* //这里的ptr是一个链表的头节点，这个宏就是取得这个链表第一元素的所指结构体的首地址
*
* list_first_entry - get the first element from a list
* @ptr: the list head to take the element from.
* @type: the type of the struct this is embedded in.
* @member: the name of the list_struct within the struct.
*
* Note, that list is expected to be not empty.
*/
#define list_first_entry(ptr, type, member) \
list_entry((ptr)->next, type, member)
/************************************************************************************************************/
/***************************************************遍历宏***************************************************/
/************************************************************************************************************/
/**************************************************list_for_each*********************************************/
/*****************************************************遍历链表***********************************************/
/**
* list_for_each - iterate over a list
* @pos: the &struct list_head to use as a loop cursor.
* @head: the head for your list.
*/
/*
* //这个实际上就是一个for循环，从头到尾遍历链表。prefetch()用于预取以此提高效率
* static inline void prefetch(const void *ptr)
* {
* __asm__ __volatile__(
* "pld\t%a0"
* :
* : "p" (ptr)
* : "cc");
* }
* #define list_for_each(pos, head) \
* for (pos = (head)->next; prefetch(pos->next), pos != (head); \
* pos = pos->next)
*/
#define list_for_each(pos, head) \
for (pos = (head)->next; pos != (head); pos = pos->next)
/*************************************************__list_for_each********************************************/
/**
* __list_for_each - iterate over a list
* @pos: the &struct list_head to use as a loop cursor. //@pos : struct list_head 类型
* @head: the head for your list.
*
* This variant doesn't differ from list_for_each() any more.
* We don't do prefetching in either case.
*/
#define __list_for_each(pos, head) \
for (pos = (head)->next; pos != (head); pos = pos->next)
/************************************************list_for_each_prev******************************************/
/*************************************************从尾到头遍历链表*******************************************/
/**
* //
* list_for_each_prev - iterate over a list backwards
* @pos: the &struct list_head to use as a loop cursor.
* @head: the head for your list.
*/
#define list_for_each_prev(pos, head) \
for (pos = (head)->prev; pos != (head); pos = pos->prev)
/************************************************list_for_each_safe******************************************/
/***************************************从头到尾遍历链表，便于删除结点***************************************/
/**
* 1.这个实际上就是一个for循环，从头到尾遍历链表。这里使用了n来记录pos的下一个，这样处理完一个流程之后再
* 赋给pos，避免了删除pos结点造成的问题，由它的英文注释我们可以看书，其实这个函数是专门为删除结点是准备的
* 2.注：list_for_each(pos, head)和list_for_each_safe(pos, n, head)都是从头至尾遍历链表的，但是对于前者来
* 说当操作中没有删除结点的时候使用，但是如果操作中有删除结点 的操作的时候就使用后者，
* 对于后面代safe的一般都是这个目的
*
* list_for_each_safe - iterate over a list safe against removal of list entry
* @pos: the &struct list_head to use as a loop cursor.
* @n: another &struct list_head to use as temporary storage
* @head: the head for your list.
*/
#define list_for_each_safe(pos, n, head) \
for (pos = (head)->next, n = pos->next; pos != (head); \
pos = n, n = pos->next)
/********************************************list_for_each_prev_safe*****************************************/
/****************************************从尾到头遍历链表，便于删除结点**************************************/
/**
* list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
* @pos: the &struct list_head to use as a loop cursor.
* @n: another &struct list_head to use as temporary storage
* @head: the head for your list.
*/
#define list_for_each_prev_safe(pos, n, head) \
for (pos = (head)->prev, n = pos->prev; \
pos != (head); \
pos = n, n = pos->prev)
/************************************************list_for_each_entry****************************************/
/**************************************************从头到尾遍历链表*****************************************/
/********************************head是一个链表，链表的每一个结点又是一个结构体*****************************/
/**
* //head链表的每个结点为pos所指向结构体的member
*
* _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
* | pos |
* | _ _ _ _ _ _ _ |
* | | | | | | | | | | | | | | | |
* | _ |_| |_| |_| |_| |_| |_| |_| |
* ---| |->| |->| |->| |->| |->| |->| |->| |<--|
* ---->|_|<-|_|<-|_|<-|_|<-|_|<-|_|<-|_|<-|_|------|
* | head member |
* |_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|
*
* list_for_each_entry - iterate over list of given type
* @pos: the type * to use as a loop cursor. //@pos : 用于遍历的指针,struct list_head类型
* @head: the head for your list. //@head: 链表头,list_head结构
* @member: the name of the list_struct within the struct. //@member : list_head在结构体当中的变量的名字
*/
#define list_for_each_entry(pos, head, member) \
for (pos = list_entry((head)->next, typeof(*pos), member); \
&pos->member != (head); \
pos = list_entry(pos->member.next, typeof(*pos), member))
/******************************************list_for_each_entry_reverse**************************************/
/**************************************************从尾到头遍历链表*****************************************/
/********************************head是一个链表，链表的每一个结点又是一个结构体*****************************/
/**
* list_for_each_entry_reverse - iterate backwards over list of given type.
* @pos: the type * to use as a loop cursor.
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*/
#define list_for_each_entry_reverse(pos, head, member) \
for (pos = list_entry((head)->prev, typeof(*pos), member); \
&pos->member != (head); \
pos = list_entry(pos->member.prev, typeof(*pos), member))
/******************************************list_for_each_entry_continue**************************************/
/*********************************************可以从指定的pos结点遍历****************************************/
/**
* list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
* @pos: the type * to use as a start point
* @head: the head of the list
* @member: the name of the list_struct within the struct.
*
* Prepares a pos entry for use as a start point in list_for_each_entry_continue().
*/
#define list_prepare_entry(pos, head, member) \
((pos) ? : list_entry(head, typeof(*pos), member))
/**
* list_for_each_entry_continue - continue iteration over list of given type
* @pos: the type * to use as a loop cursor. //@pos : 用来存储结构体首地址，不同于list_for_entry中的pos
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*
* Continue to iterate over list of given type, continuing after
* the current position.
*/
#define list_for_each_entry_continue(pos, head, member) \
for (pos = list_entry(pos->member.next, typeof(*pos), member); \
&pos->member != (head); \
pos = list_entry(pos->member.next, typeof(*pos), member))
/***************************************list_for_each_entry_continue_reverse**********************************/
/********************************************可以从指定的pos结点向前遍历**************************************/
/**
* list_for_each_entry_continue_reverse - iterate backwards from the given point
* @pos: the type * to use as a loop cursor.
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*
* Start to iterate over list of given type backwards, continuing after
* the current position.
*/
#define list_for_each_entry_continue_reverse(pos, head, member) \
for (pos = list_entry(pos->member.prev, typeof(*pos), member); \
&pos->member != (head); \
pos = list_entry(pos->member.prev, typeof(*pos), member))
/********************************************list_for_each_entry_from****************************************/
/***********************************************从当前结点开始遍历*******************************************/
/**
* list_for_each_entry_from - iterate over list of given type from the current point
* @pos: the type * to use as a loop cursor.
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*
* Iterate over list of given type, continuing from current position.
*/
#define list_for_each_entry_from(pos, head, member) \
for (; &pos->member != (head); \
pos = list_entry(pos->member.next, typeof(*pos), member))
/********************************************list_for_each_entry_safe****************************************/
/**************和list_for_each_entry的遍历类似，这个带了safe是为了防止删除节点而造成断链的发生***************/
/**
* list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
* @pos: the type * to use as a loop cursor.
* @n: another type * to use as temporary storage //@n : n是为了防止删除节点而造成断链的发生
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*/
#define list_for_each_entry_safe(pos, n, head, member) \
for (pos = list_entry((head)->next, typeof(*pos), member), \
n = list_entry(pos->member.next, typeof(*pos), member); \
&pos->member != (head); \
pos = n, n = list_entry(n->member.next, typeof(*n), member))
/****************************************list_for_each_entry_safe_continue************************************/
/************和
list_for_each_entry_continue()遍历类似，这个带了safe是为了防止删除节点而造成断链的发生*********/
/**
* list_for_each_entry_safe_continue - continue list iteration safe against removal
* @pos: the type * to use as a loop cursor.
* @n: another type * to use as temporary storage
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*
* Iterate over list of given type, continuing after current point,
* safe against removal of list entry.
*/
#define list_for_each_entry_safe_continue(pos, n, head, member) \
for (pos = list_entry(pos->member.next, typeof(*pos), member), \
n = list_entry(pos->member.next, typeof(*pos), member); \
&pos->member != (head); \
pos = n, n = list_entry(n->member.next, typeof(*n), member))
/**
* list_for_each_entry_safe_from - iterate over list from current point safe against removal
* @pos: the type * to use as a loop cursor.
* @n: another type * to use as temporary storage
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*
* Iterate over list of given type from current point, safe against
* removal of list entry.
*/
/******************************************list_for_each_entry_safe_from**************************************/
#define list_for_each_entry_safe_from(pos, n, head, member) \
for (n = list_entry(pos->member.next, typeof(*pos), member); \
&pos->member != (head); \
pos = n, n = list_entry(n->member.next, typeof(*n), member))
/**
* list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
* @pos: the type * to use as a loop cursor.
* @n: another type * to use as temporary storage
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*
* Iterate backwards over list of given type, safe against removal
* of list entry.
*/
/******************************************list_for_each_entry_safe_reverse**************************************/
/**************************************和
list_for_each_entry_safe_from方向相反***********************************/
#define list_for_each_entry_safe_reverse(pos, n, head, member) \
for (pos = list_entry((head)->prev, typeof(*pos), member), \
n = list_entry(pos->member.prev, typeof(*pos), member); \
&pos->member != (head); \
pos = n, n = list_entry(n->member.prev, typeof(*n), member))
/**********************************************list_safe_reset_next**********************************************/
/******************************************************重设******************************************************/
/**
* list_safe_reset_next - reset a stale list_for_each_entry_safe loop
* @pos: the loop cursor used in the list_for_each_entry_safe loop
* @n: temporary storage used in list_for_each_entry_safe
* @member: the name of the list_struct within the struct.
*
* list_safe_reset_next is not safe to use in general if the list may be
* modified concurrently (eg. the lock is dropped in the loop body). An
* exception to this is if the cursor element (pos) is pinned in the list,
* and list_safe_reset_next is called after re-taking the lock and before
* completing the current iteration of the loop body.
*/
#define list_safe_reset_next(pos, n, member) \
n = list_entry(pos->member.next, typeof(*pos), member)
/*
* Double linked lists with a single pointer list head.
* Mostly useful for hash tables where the two pointer list head is
* too wasteful.
* You lose the ability to access the tail in O(1).
*/
#endif